Circuit breaker with improved venting means and arc extinguishing structure



Aprll 14, 1970 J. P. ELLSWORTH ET AL 3,506,799

- CIRCUIT BREAKER WITH IMPROVED VENTING MEANS AND ARC EXTINGUISHING STRUCTURE Flled June 23, 1967 2 Sheets-Sheet 1 INVENTORS domes P. Ellsworth and 8 Glenn R. Thomas WM a. 560M ATTORNEY April 14, 1970 Y J. P. -ELLSWORTH ET AL 3,506,799

CIRCUIT BREAKER WITH IMPROVED VENTING MEANS AND ARC EXTINGUISHING STRUCTURE Filed June 25, 1967 2 Sheets-Sheet 2 FIG.4.

VFIG.9.

I79 :79 L I J United States Patent CIRCUIT BREAKER WITH IMPROVED VENTING MEANS AND ARC EXTINGUISHING STRUCTURE James P. Ellsworth and Glenn R. Thomas, Beaver, Pa.,

assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 23, 1967, Ser. No. 648,288 Int. Cl. H01h 9/44 US. Cl. 200-147 Claims ABSTRACT OF THE DISCLOSURE A circuit breaker comprises an improved arc-extinguishing structure and improved means for venting arc gases from the breaker housing.

CROSS-REFERENCES TO RELATED APPLICATION Certain parts of the herein-disclosed circuit breaker are disclosed and claimed in our copending patent application Ser. No. 648,431, filed concurrently herewith.

BRIEF SUMMARY OF THE INVENTION A molded case type circuit breaker comprises an insulating housing and an arc-extinguishing structure, comprising a plurality of spaced magnetic plates, at the back and at one end of the housing. The housing is molded to form improved vent passages for venting arc gases from the arc-extinguishing structure out of the housing. The arc-extinguishing structure comprises a pair of magnetic plates that are longer than other of the magnetic plates, and the housing is formed to accommodate the longer magnetic plates. The arcs are drawn into the plates toward the housing, and the housing comprises a molded insulating material that has good physical strength, good electrical insulating properties and that provide advantageous arc-suppressing and arc-quenching characteristics.

An object of this invention is to provide an improved molded-case type circuit breaker comprising improved means for venting arc gases from the breaker housing.

Another object of this invention is to provide an improved circuit breaker comprising an improved arc-extinguishing structure. The further object of this invention is to provide an improved circuit breaker with improved means for extinguishing arcs drawn between the contacts by magnetically drawing the arcs toward the housing which housing comprises a molded material that has good physical strength, good electrical insulating properties and that provides advantageous arc-suppressing and arc-quenching characteristics.

Another object of this invention isto provide an improved compact circuit breaker having an increased ratmg.

The invention, both as to structure and operation, together with additional objects and advantages thereof, will best be understood from the following detailed description when read in conjunction with the accompanying drawings.

In said drawings:

FIGURE 1 is a top plan view of a circuit breaker embodying principles of this invention;

FIG. 2 is a side view, with the side cover plate removed and with the arc-extinguishing structure shown in section, of the circuit breaker seen in FIG. 1;

FIG. 3 is an end view of the circuit breaker-seen in FIG. 2 with the cover plate in position and looking in the direction of theIII-III arrows of FIG. 2;

FIG. 4 is an end view similar to FIG. 3 taken from the opposite end of the circuit breaker of FIG. 2;

FIG. 5 is a side elevational view of the arc-extinguishing structure seen in FIG. 2;

FIG. 6 is a top plan view of the arc-extinguishing structure of FIG. 5;

FIG. 7 is a sectional view taken along the line of VII VII of FIG. 6;

FIG. 8 is an end view of the arc-extinguishing structure of FIG. 7 looking in the direction of the VIIVII arrows in FIG. 7;

FIG. 9 is an elevational view of one of the magnetic plates of the arc-extinguishing structure before the plate is assembled in the arc-extinguishing structure.

FIG. 10 is a sectional view taken generally along the line X-X of FIG. 2 with the housing part 9 (FIG. 1) secured to the housing part 7 seen in FIG. 2; and

FIG. 11 is a sectional view taken along the line XIXI of FIG. 2 with the housing part 9 secured to the housing part 7 seen in FIG. 2.

Referring to the drawings, there is shown, in FIGS. 1-4, a circuit breaker 3 comprising an insulating housing 5. The housing 5 comprises a molded insulating housing part 7 and a molded insulating cover part 9. The housing part 7 is an open-sided member having a cavity into which the circuit breaker mechanism 11 is positioned during the assembly of the breaker. Thereafter, the cover part 9 is placed in position and three rivets are passed through three openings 13 (FIG. 2) in the housing parts 7 and 9 to secure the housing parts together. The circuitbreaker housing 5 comprises a front 15 (FIG. 1), a back 17 (FIG. 2), two end walls 19 (FIG. 1) and two sidewalls 21.

The circuit-breaker mechanism 11 comprises a station ary contact 23, a movable contact 25, an operating mechanism 27, a trip device 29 and an arc-extinguishing structure 31.

The stationary contact 23 is fixedly secured to the inner end of a bolt-on type terminal conductor 33 that extends out through an opening or terminal opening means 35 in the housing 5 and that is bent over to provide a generally flat connecting part 37 having an opening 39 therein. When the circuit breaker is mounted on a panelboard, the part 37 of the terminal engages a fiat conductor in the panelboard, and a bolt is passed through the opening 39 to fixedly secure the terminal 33 to the panel-board conductor. At the opposite end of the housing 5, a terminal conductor 41 extends out through an opening 43 in the housing 5 into a cavity as shown, and a screw-type solderless terminal connector 45 is connected to the outer end of the terminal 41 to permit connection of the terminal 41 to a conducting line at the panelboardinstallation..'I'he terminal 45 is provided with a screw 47 for pressure connecting the conducting line to the terminal 41 in a manner well known in the art. I

The movable contact 25 is fixedly secured to a conduct ing extension 49 that is fixedly secured to a U-shaped conducting contact arm 51. A molded insulating operating member 53 is provided-with a pair of pins 55 (only 'one of which is seen in FIG. 2) that are molded integral with the member 53 at opposite sides of the member 53. The pins 55 move in a pair of openings 57 in he opposite sidewalls of the housing 5. The upper ends-of the legs of the U-shaped contact arm 51 pivotally engage the operating member 53 at pivot surfaces 59 that are provided in recesses in the operating member 53. The operating member 53 comprises anarcuate-shield -part .61 and a handle part 6 3-As canbe seen in FIGS. 1 and 2., the insulating housing 5 is provided with an opening 65 at thefront 15 of the housing, and the operating member-53; is positioned at theopening with the handle part 63protruding out through the opening and with the arcuateshield part 61 closing the opening in all positions of the operating member 53. The front 15 of the insulating housing is provided with a pair of arcuate surfaces 67 that are engaged by the arcuate shield part 61 of the operating member 53 in a manner to be hereinafter described.

An overcenter operating spring 71 is connected, under tension, at the back end thereof in a suitable opening in the bight portion of the U-shaped contact arm 51 and at the front end thereof in a suitable opening in a trip member 73. The spring 71 moves between the legs of the U-shaped contact arm 51. The trip member 73 is pivotally supported at one end thereof on the sidewalls of the housing 5 by means of a pivot pin 75. The other end 77 of the trip member 73 extends into a window-opening in a latch member 79, and engages on a ledge in the windowopening of the member 79 in the latched position seen in FIG. 2.

The latch member 79 is a part of the trip device 29. The latch member 79 is an elongated metallic member having a pair of cars 81 (only one of which is seen in FIG. 2) at the opposite sides thereof that are positioned in V-shaped openings 83 in the opposite sidewalls of the housing 5 to pivotally support the member 79. A spring 85 biases the latch member 79 in a clockwise (FIG. 2) direction to the latching position seen in FIG. 2. The latch member 79 comprises an elongated latching leg 87 that is bent over at the lower end thereof to provide a short leg 89 that is positioned on the opposite side of one leg of a U-shaped bi-metal 91 that is fixedly secured at one end thereof to the terminal conductor 41. A U-shaped magnetic member 93 is secured at the lower free end of the bimetal 91 with the opposite legs thereof facing an armature portion 95, of magnetic material, of the latch member 79. An insulating button 97 is fixed to the back of the U-shaped magnetic member 93 to engage the leg 89 of the latch member 79. An adjusting screw 99 is threaded into a nut 101 that is captured in the housing. The screw 99 can be rotated to adjust the initial position of the bimetal 91 to thereby calibrate the circuit breaker. A suitable cement may be used to close off the opening in back of the adjusting screw after the circuit breaker is calibrated.

In the closed position of the contacts, the circuit extends from the terminal 33 through the contact 23, the contact 25, the conducting extension 49, the contact arm 51, a flexible conductor 103 that is connected at one end of the contact arm 51 and at the other end to the lower free end of the bimetal 91, through the bimetal 91, the terminal 41, to a conducting line that would be connected to the terminal 41 by means of the solderless terminal connector 45.

The contacts are manually closed by counterclockwise movement of the operating member 53, in a manner to be hereinafter described, about the axis of the pivot pins 55 from the o to the on position. This movement, due to the pivotal engagement between the ends of the legs of the contact arm 51 with the pivot surfaces 59 of the operating member 53, moves the upper end of the contact arm 51 to the right of the line of action of the spring 71 whereupon the spring 71, which has been additionally stretched during this movement, is positioned overcenter relative to the contact arm 51 and biases the contact arm 51 to the closed position with a snap-action. The contacts are manually opened by reverse movement of the operating member 53 from the on to the o position. This movement, through the pivotal engagement of ends of the legs of the contact arm 51 with pivot surfaces 59, moves the upper end of the contact arm 51 to the left of the line of action of the spring 71, during which movement the spring 71 is additionally stretched, whereupon the spring 71 is positioned overcenter relative to the contact arm 51 and biases the contact arm 51 to the open position seen in FIG. 2 with a snap-action. Movement of the contact arm 51 to the open position is limited by the engagement of the contact arm with a 4 projection 105 that is molded integral with the housing part 7.

When the circuit breaker 3 is in the closed position, and a persistent overload above a predetermined value of, for example, less than ten times normal rated current occurs, the trip device 29 operates thermally to effect a tripping operation. During this thermal tripping operation, which occurs with a time delay, the bimetal 91 flexes to the right, whereupon the insulating button 97 at the lower free end thereof engages the short leg 89 of the member 79 moving the member 79 in a counterclockwise direction about the pivots 81 to release the free end 77 of the releasable trip member 73. Upon release of the trip member 73, the spring 71 biases the trip member in a counterclockwise direction about the pivot 75 to a posi tion wherein the trip member 77 engages the projection 105 on the circuit-breaker housing. During this movement, the line of action of the spring 71 is moved from the left of the closed contact arm 51 to the right of the contact arm 51 and the spring 71 contacts to move the contact arm 51 to the tripped position seen in FIG. 3. During this movement, the spring 71 operates to move the operating member 53 to a tripped position intermediate the on and off positions to provide a visual indication, in a manner well known in the art, that the circuit breaker has tripped open. During this movement, an are drawn between the contacts 23 and 25 is extinguished in the arc-extinguishing structure, and the are gases escape through a vent passage 107 that leads out of one end of the circuit breaker and through another vent passage 109 that leads out the other end of the circuit breaker.

The circuit breaker is trip-free in that the breaker will trip open even if the operating handle 63 is manually held in the on position.

When an overload current above ten times the normal rated current, or a short circuit current, occurs, the trip device 29 operates electromagnetically to trip the circuit breaker instantaneously. Upon the occurrence of the overload above ten times normal rated current, the current flowing through the bimetal 91 energizes the magnetic parts 93, 95 sufficiently so that the magnetic part 95 of the trip member 79 is attracted toward the magnetic member 93, independent of movement of the bimetal 91, to release the trip member 73. Upon release of the trip member 73 the circuit breaker is stripped open in the same manner as was hereinbefore described with regard to the thermal tripping operation.

After each tripping operation, the circuit breaker is reset and relatched by movement of the operating member 53 from the intermediate position to a position slightly past the full off position. During this movement, a lower leg portion 110 of the Operating member 53 engages a pin 111 on the trip member 73 to rotate the trip member 73 counterclockwise about the pivot 75. When the trip member 73 reaches the position seen in FIG. 2, the spring 85 biases the latch member 79 clockwise to the latching position shown. Thereafter, upon release of the operating member 53 the circuit breaker is latched. Thereafter, the circuit breaker can be operated in the same manner as was hereinbefore described.

In the on, off and tripped positions of the circuit breaker 3, the operating spring 71 is under tension between the trip member 73 and the contact arm 51. 'In these positions, the spring 71 tends to pull the trip member 73 downward (FIGS. 2 and 3) which movement is limited in the on and off positions because the trip member 73 is latched and which movement is limited in the tripped position (FIG. 3) because the trip member 73 engages the projection 105. Since the spring 71 is under tension in these positions, the spring pulls the contact arm 51 frontward, and because the contact arm 51 engages the surfaces 59 of the operating member 53, this force of the spring 71 operates through, the contact arm 51 to bias the operating member 53 frontward where the arcuate shield part 61 of the operating member 53 engages the are disposed.

inner arcuate surfaces 67 (FIG. 4) of the front part of the insulating housing 5 at two opposite sides of the opening 65: This movement is permitted because the openings 57 (FIG. 4) in the sidewalls 21 of-the hous ng 5 are elongated in the direction from back to front and large enough to permit limited movement of the pivot pins 55 of the operating member 53- in the openings 57. During automatic tripping operations, the pressure of the arcgases that are generated in the arc-extinguishing structure 31 serves to additionally bias the operating member 53 into engagement with the surfaces 67 to provide increased sealing pressure even through the gas pressure is quickly relieved when the gases move out through the vent passages 107, 109. During an automatic tripping operation, the trip member 73, contact arm 51 and operating member 53 are moved to the intermediate tripped position with the arcuate shield surface 61 of the operating member '53 riding along the arcuate surfaces 67 of the housing 5 During this movement the pressure within the housing and the operating spring 71 serves to bias the arcuate shield part 61 of" the operating member'53 against the arcuate surfaces 67 of the housing 5 to limit passage of gases out through the front opening 65.

"iThe manual'operation can occur in three slightly different'ways. If no downward pressure is applied to the operating member 53, the'arcuate shield part 61 will ride along the arcuate surfaces 67 on the front of the housing moving about the axis of the pins 55 during the manual operations. If a limited amount of downward pressure is applied to the operating member 53, the operating member will essentially be moved away from the arcuate surfaces 67 and the member 53 will essentially float during the pivoting action about the axis of the pins 55 with thearcuate shield part'61 being spaced a slight distance 21101111116 surfaces 67 of the front of the housing. If an additional amount of downward pressure is applied to the operating member 53, the bottom surfaces of the pins 55 will engage the bottom surfaces of the openings 57 (FIG. 4) which surfaces limit downward movement of the operating member 53, and the operating member 53 will pivotabout the lowered axis of the pins 55. During the automatic tripping operations, since there is no manual force being applied to the operating member 53,'it can be understood that the arcuate shield surface 61 will ride against the arcuate surfaces 67 of the housing with the operating member'53 pivoting about the axis of the pins '55 which pins 55 will be in the upper position seen in *As can be seen in FIGS. 4, 5 and 6, the operating member 53 is formed with arcuate surfaces 113 that are "positioned close to, but spaced sl ghtly from, arcuate surfaces 114 on the front of the housing. Although the surfaces-113, 114 do not engage when the operating member 53 is in the uppermost position, it can be understood with reference toFIG. 6 that gases and/or particles must move through a tortuouspath to leave the housing at these areas. These surfaces 113, 114 are spaced very slightly because it isimportant thatthe surfaces 61, 67 engage. Because of manufacturing tolerances the slight spaces are provided between the surfaces 113, 114 toinake sure that there will be no engagement be tween'the surfaces 113, 114 that might interfere with the ,engagement between the surfaces 61, 67. Resilient packingor sealing .materialcould be positioned between the member 53 and the housing front at the two sides of the handle opening opposite thetwo sides where the surfaces \;As can be seen in F-IGS. 2 and 5-8, the arc-extinguishings structure 31 comprises an insulating wrapper support 119' and a plurality of flat magnetic plates 121, 123 supported on the support 119 The wrapper support 119 is generally U-shapedin'const'ruction comprising a pair of leg parts 125and a bight part 127 that is formed with an opening 131 for receiving the contact arm 51 and an opening 133 forreceiving gases that flow through the vent 6 passage 109 (FIG. 2). As can be seen in FIG. 7, the wrapper support 119 comprises two layers comprising a stiff insulating outer layer 137 and an inner layer 139 of asbestos that is suitably cemented to the layer 137. The outer layer 137 is stiff to support the plates 121, 123 and the inner layer 139 is provided for increased heat resistance. As can be understood with reference to FIGS. 5-9, each of the magnetic plates 121, 123 is a fiat plate of magnetic material with the plates 121, 123 being similar in construction except that the plates 123 are longer. Each of the magnetic plates 121, 123 is a generally U-shaped plate member with a slot 141 (FIG. 9) therein and with two projections 143 extending outward from each of the two legs of the plate. The wrapper support 119-is provided with openings in the opposite legs thereof for receiving the projections 143 of the plates 121, 123. During the assembly of the arc-extinguishing structure 31, the plates 121, 123 are mounted within the wrapper support 119 with the projections 143 extending through the openings in the side walls 125, and thereafter the projections 143 are riveted over to thereby secure the plates 121, 123v on the wrapper support 119. As can be understood with reference to FIGS. 5-8, the slots 141 are aligned and the movable contact 25 (FIG. 2) moves through the slots 141. As can be understood with reference to FIGS. 7 and 8, the U-shaped wrapper support 119 is open at both ends and at the bottom of the arc-extinguishing structure.

As was previously set forth, the insulating housing 5 comprises the open-sided housing part 7, formed with a cavity therein for receiving the circuit-breaker mechanism, and the cover housing part 9 which parts are riveted together to enclose and support the circuit-breaker mechanism.

The housing part 9 is formed with projections 147 and 149 (FIG. 10) that are molded integral with the housing. The projection 147 cooperates with a similar projection 151 on the housing part 9 to provide the upper wall of the vent passage 107, and the projection 149 cooperates with a similar projection 153' on the housing part 9 to provide the back of the insulating housing. As can be seen in FIG. 10, the side walls of the circuit breaker are side walls of the vent passage 107. The projections 147, 151 provide the top wall and the projections 149, 153 provide the back wall of the vent passage 107. As can be seen in FIGS. 2 and 3, the vent passage 107 extends from the open end of the arc-extinguishing structure 37 to the end of the housing that is opposite the end where the arcextinguishing structure 31 is disposed. The vent passage 107 leads out under the terminal 45. As can be understood with reference to FIG. 2, the projection 147 extends over to the end of the housing 2 and downward at the very end of the housing to keep the gases away from the terminal 45.

-As can be understood with reference to FIGS. 2 and 11, the housing part 7 is formed with projections 157 and 159 molded integral therewith. The projection 157 cooperates with a similar projection 161 on the housing part 9 and a projection 159 cooperates with a similar projection 163 on the housing part 9 to form'the vent passage 109. As can be understood with reference to FIGS. 2, 4, 6, 7 and 11, are gases can escape from the arc-extinguishing structure 31 through the opening 133 in the wrapper support 119 of the opening 133 which leads to the vent passage 109 above the stationary contact 23, and which vent passage 109 leads out of the end of the circuit breaker above the stationary contact 23. As can be understood with reference to FIGS. 2 and 11, the projections 157, 161 form the top wall of the vent passage 109. The projections 157, 161 block the gases from moving straight up from the stationary contact and they funnel the gases into the vent passage 109. With the extension 49 on the contact arm 51, the contacts are positioned under the throat of the vent passage 109 in the closed position and the top wall'157, 161 of the vent passage does not interfere with movement of the contact arm 51 to the closed position. When the circuit tween the separating contacts are forced out of the opposite ends of the breaker under pressure through the vents As can be seen in FIG. 2, the back 17 of the insulating housing is formed with a lower part 171 from one end of the breaker to the area of the arc-extinguishing structure, a slightly lower part 173 under the magnetic plates 121' and a lower part 175 under the longer magnetic plates 123. The lowermost part 175 is positioned above the lowermost part of the terminal 37 so as to not inter-- fere with the mounting operation of the terminal 37 on a flat conductor, and the part 171 is elevated relative to the lowermost part 175 to fit on suitable ledges of a panelboard at the installation. Thus, the housing 5 is provided with a lower protuberance or compartment part to accommodate the two longer magnetic plates 123,

which protuberance occupies panelboard space that wascontacts, and the yoke portion of the right-hand arc plate (FIG. 2) is disposed adjacent the throat of the vent passage 107. The bottom corners of the arc plates 121, 123 are notched or shortened at the edges 179 (FIG. 9) to provide vent passages (between the lower corner parts or edges 179 of the magnetic plates and the housing) for permitting the gases to move between the edges 179 and housing into the vent passage 107 (FIG. 2). As can be seen in FIG. 2, the lowermost parts or back ends of the plates 121, 123 are spaced slightly from the back part of the housing to permit gases to move along the back under the arc plates into the vent passage 107. The slanting of the arc plates 121, 123, and the provision for permitting the gases to move with relative freeness into the throat of the vent passage 107, provides a good venting action of the gases through the vent passage 107 to thereby limit the passage of the gases into the space around the circuit breaker operating mechanism. As can be understood with reference to FIGS. 2 and 11, the provision of the additional vent passage 109 above the stationary contact, with the top wall of the vent passage 109 funneling the gases into the vent passage 109, aids in limiting the movement of gases into the area of the circuit breaker mechanism.

The molded housings 7 and 9 are characterized by the presence of a substantial proportion of an oxide or hydrate of aluminum in its composition. The composition of the molding material includes a suitable organic binder and a filler, the aluminum oxide or hydrate constituting an ingredient of the filler.'The binder comprises from 5% to 75% by weight of the total composition. The filler comprises from 95% to 25% by weight of the total compositiomThe filler comprises glass fibers, asbestos, or the like in combination with the aluminum oxide or hydrate.

The oxide or hydrate comprises from 5% to 90% of the total composition, and the glass or asbestos from 20% to 5%of the total composition.

Four illustrative examples are the following:

valumina, which requires about 3 7003 1 for its formatiQ l,..-;

vis released when the ,arcnstrikee,

In addition to or in place of a polyester resin, other i resins, for example, phenolic, urea melamine, and; sili cone resins maybe employed as the, binder portion of the r molding composition. N a

The active arc-suppressing.ingredients, namely the alu minoxide or hydrate, in the above. examples. maybe used in commercial grades-The aluminumhydrates have the composition indicatedby the formula Al o 'eil-l o or.. Al(OH) Aluminum oxide suitable for use in ourco nf positions may be a commercial calcinedor tabular, a1u.- mina, usually an aluminum-hydrate calcined or heated to. 1800 3500? F., but preferably hasnot been fused, Fused exists as crystals which are abrasive in; character and r sult inexcessive wear of molds. In cold-molding arc-suppressing devices employingl orm ganic binders, theingredients are preferahly firstblended in a dry. statee-The blended; dry mixtu re is then wetted' L with an agent. capableof liquifying or, sofitening; th binder, and mixing is continued.v The wet mixture then granulated andmolded under pressure into.the ,de.- sired shape-Followingthe molding operatiom the device are cured in baking ovens under,elevatedtemperature which gradually increases to a maximum of 300s toi 400 F. I I Compositions embodying organic bindersmay alter natively be made bya hot-moldingprocess. In that event 'a wet mixture produced as above set forth wouldhej dried before granulating, and the dry granular product; molded into an article of the desired form under hleat 1 and pressure, as in conventional compression-.mo ldin methods. Since fluidityof a hot-molded mixture depends on softening of the binder, the binder content of -1.1ch-- mixtures should preferably not be lessthan about 35% The aforesaid moldingv material of the: housingapartsw 7 and 9 has good physical strength for resisting the forces 1 of gas pressure within the housing during the. circuit interruption. The molded materialalso has goodelectricah insulating properties such that the materialresistssurface-- tracking or the tendency of organic substancestowcarbonize on the surface of the .materialtoform a conduel tive path. Moreover, during circuitinterruption athe'ama-a terial has the advantage of releasing .water and carbon: forming carbonmonoxide (CO) carbonadioxide (CO and water in gaseous form tosuppressthe ares, Th ld, ed material also has a regenerative characteristic in that, it will absorb water toreplenish, the supplier watenthat-lr When the circuit breakeris in theclosed phenome a a tripping overload occurs, the movablelcontact .51, is moved from the-closed ,position, -to the open positioni in the manner hereinbefore described. During-this movefiq ment, the contact arm 51 moves in, the Slot 131 (FI G{6,). in the wrapper support 119.and themovable contact :25 moves from the closed to the open position in thefaligned slots 141. (FIGS. 8 and 9 in the magnetic plates l 1 123, During this movement, the at that is establis edbefl;

. tween the. contacts 23, 25v is attracted .magnetically dow f into the slots 141 and into the bightportiqns of them-agnetic plates 121, 123 where the arcis split. up into a plural-Q ity of serially related are portions .bet weenthe l spaced. plates 121, 123 where the arc is cooledand-wriapidly extin-f guished. As can be seen in FIGS. 2and 8,,tjhe wrappersup port 119 is open at the bottom so that as the are is drawn downward into the magnetic plates the arc moves toward the bac of the insulating housing causing gas to evolve from the housing material in'the form of carbon monoxide (CO), carbon dioxide (CO and water which gas increases the speed of arc interruption and reduces erosion. The step part 180 (FIG. 2) provides increased gas-evolving surface, and the part 180 also provides a tortuous path'for arcs should there bea tendency of the arcs to re-strike in back of the plates. During the circuit interruption, the arc gases are vented out of the vent passages 107, 109 in the manner hereinbefore described. I I

Circuit breakers rated at 15 amperes, circuit breakers rate at 20 amperes and circuit breakers rated at 30 amperes, all constructed in accordance with the hereindescribed invention, have been successfully tested to interrupt 10,000 amperes at 277 volts. These tested circuit breakers :were one-inch wide breakers having external dimensions similar to other standard 120/240 volt breakers. Thus, with these new breakers, 277 volt panelboards can be made the same size as certain standard 120/ 240 volt panelboards.

Since numerous changes may be made in the abovedescribed construction and because different embodiments of the invention may be made without departing from the spirit and scope of the invention, it is intended that all of the matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. A circuit breaker comprising a molded insulating housing comprising a front, a back, a pair of opposite side walls and a pair of opposite end walls, said front having a handle-receiving opening therein, a circuitbreaker mechanism supported in said housing, said mechanism comprising an arc-extinguishing structure in proximity to one end of said housing, said arc-extinguishing structure comprising a plurality of generally flat magnetic plates, each of said plates having a slot therein open at the front end of the plate, means supporting said plates in a face-to-face relationship with said slots in general alignment in the direction from said one end toward the other end of said housing and with the back ends of said plates in proximity to the back of said housing, said mechanism comprising a stationary contact at said one epd of said housing, said housing having terminal opening means therein, a bolt-on type terminal conductor carrying said stationary contact thereon inside of said housing and extending out of said housing through said terminal opening means, a movable contact, a contact arm carrying said movable contact and movable to move said movable contact in said aligned slots from a closed position in a direction toward said other end of said housing to an open position, said housing being molded to form a first vent passage open from said arc-extinguishing structure to said other end of said housing for venting gases out of said other end, and said housing being molded to form a second vent passage open from said arc-extinguishing structure out of said one. end of said housing for venting gases out of said one end.

2. A circuit breaker according to claim 1, said first vent passage starting in proximity to the magnetic plate that is closest to said other end of said housing and extending generally along the back of said housing to said other end, and said second vent passage starting generally above said stationary contact and extending out of said one end of said housing.

3. A circuit breaker according to claim 2, said housing comprising an open-sided housing part and a side cover part, said open-sided housing part and said side cover part comprising molded parts matingto form said first and second vent passages.

4. A circuit breaker according to claim 3, and said spaced magnetic plates being slanted toward said first vent passage to direct gases into said first vent passage and out of said other end of said housing.

5. A circuit breaker according to claim 3, said opensided housing part and said side cover part each' being a molded insulating material composition comprising a water-insoluble binder and an arc-suppressing substance selected from the group consisting of the oxides and hydrates of aluminum, said binder constituting at least 5% by weight of the total composition, and said areextinguishing structure being open between the back ends of said plates and the back of said housing.

6. A circuit breaker according to claim 4, said arcextinguishing structure comprising a plurality of shorter magnetic plates positioned closest to said first vent passage and a plurality of longer magnetic plates longer than said shorter magnetic plates positioned closest to said one end of said housing, and said housing at the back one end thereof being formed with a protuberance in the direction of the back of said housing to accommodate said plurality of longer magnetic plates.

7. A circuit breaker according to claim 6, said bolt-on type terminal conductor being bent over to form a generally flat connecting part outside of said housing extending away from said housing in the direction from said other end to said one end of said housing which connecting part is positioned below the lowermost part of said housing, and said connecting part having an opening therein for receiving securing means to enable connection of said connecting part to a generally fiat panelboard conductor.

8. A circuit breaker comprising a molded insulating housing, said housing comprising a front, a back, a pair of opposite side walls and a pair of opposite end walls, said front having a handle-receiving opening therein, a circuitbreaker ,mechanism supported in said housing, said mechanism comprising an arc-extinguishing structure comprising a plurality of generally flat magnetic plates, each of said plates having a slot therein open at the front of the plate, means supporting said plates in a face-to-face relationship with said slots in general alignment in the direction from one end toward the other end of said housing and with the back ends of said plates in proximity to the back of said housing, a stationary contact supported at said one end of said housing, a movable contact, a contact arm carrying said movable contact and movable to move said movable contact generally in said aligned slots from a closed position in a direction toward the other end of said housing to an open position, an operating member comprising a handle part protruding through said handle-receiving opening, said operating member being manually movable between operating positions to operate said contact arm to open and close said contacts, trip means operating automatically upon the occurrenceof overload current conditions above a predetermined value to eflfect movement of said contact arm to the open position, said magnetic plates comprising a plurality of shorter magnetic plates and a plurality of magnetic plates longer in the direction from front to back than said shorter magnetic plates, said longer magnetic plates being positioned adjacent each other and being the plates that are closest to said one end of said housing, and said housing being formed with a protuberance in proximity to said one end of said housing protruding in the direction away from the back of said housing to provide additional space within said housing for accommodating said longer magnetic plates.

9. A circuit breaker according to claim 8, said housing being molded to form a vent passage from said arcextinguishing structure to said other end of said housing to vent gases out of said other end of said housing, and

said magnetic plates being slanted toward said vent pas-.

of said magnetic plates and said housing.v

Refeifences Cited UNITED STATES PATENTS 6/1943 Jennings 200147 X 9/ 1962 Gcissner et a1.

3,280,287 10/1966 Ellsworth et al. 200 147 200 144, 168 v 1 ROBERT Examinen" Y a /1 69 xii 9 ,5 6. 18/1961; 

